The frequency of falls in the elderly increase in each life decade such that by the time one reaches the age of eighty, the probability of a damaging fall is about one in three. While there is evidence of a general slowing of sensory-motor processes (sensory input, response and execution) with age, the relative contribution of these processes to the increased frequency of falls in the elderly is not clear. Part I of this research specifically examines one aspect of sensory input related to falls, proprioception, to document its change with age. Further, postural sway and proprioceptive function in the lower extremities will be examined, and the relationship between them established. Subsequently, subjects with high composite postural sway scores and poor proprioceptive function will be given proprioceptive training to document the benefits of such practice and determine if postural stability is improved. Part II of the proposed research will establish whether the high incidence of falls in the elderly arises from deficits confined to the postural control system, or from a more fundamental impairment of voluntary movement in which the interplay between destabilizing voluntary actions and their accompanying postural adjustments break down. These studies will document how two distinct processes fundamental to postural control and implicated in falls change with age: proprioception and postural response organization during voluntary movement.